Does havin milk cause gas

Asked for Female, 25 Years

When my friend drinks milk in empty stomach in morning or at niight before going to bed, she develops gas issues and sometimes her stomach becomes upset. she had stopped drinking milk for 2 years and now it has been around 6 months since she began having milk again. She is facing the problem for the past 6 months. Is it beacause of the milk or something else? Any cure or precaution for the same?